High School Chemistry Water Ionization Problems, High School Chemistry Which Substances Are Ionized

HCL and NaOH are completely ionized, so the hydrogen ions in hydrochloric acid, and the hydroxide groups in NaOH are kw=c(H+)*C(OH-)=10 -14, and we can know that the concentration of hydrogen ions in NaOH is.

10 -13mol l, so the concentration of hydrogen ions in hydrochloric acid is greater than that of NaOH.

Equal. KW = C (H +) * C (OH-) = 10 -14 in solution

In HCl solution, C(H+)=, substituting the above formula, then C(OH-)=C(H+)=10 -13 is ionized by water

In NaOH solution, C(OH-)=, then C(OH-)=C(H+)=10-13 ionized from water

Generally speaking, for strong acid or alkali solutions, the effect of ionization of water itself can be ignored. For the HCl solution in the problem, C(H+) is equal to. For NaOH, its C(OH-)=, while the ionic product constant of water is 10(-14), so C(H+)=10(-14).

In acidic solution, H+ can be regarded as all acid ionization (water is also ionized, negligible), so C(H+)=C(HCl)=, all H+ in alkaline solution is ionized by water, so it cannot be omitted, according to KW=C(H+)·C(OH-)=10 14, C(H+)=14+LGC(OH-)=10 13

The acidic acid of multiple weak acids can be both ionized and alkaline.

If the degree of ionization is greater than the degree of hydrolysis, the solution is acidic, and if the degree of hydrolysis is greater than the degree of ionization, the solution is alkaline.

Ionization greater than hydrolysis is generally a strong weak acid acid acid: HSO3-, H2PO4-, etc.

Hydrolysis greater than ionization is generally weaker weak acid acid acid acid: HCO3-, HS-, etc.

1 Properties of salts.

This is an intrinsic factor affecting the hydrolysis of salts, the weaker the acid or base that makes up the salt, the greater the degree of hydrolysis of its salt, and the stronger the alkalinity or acidity of the salt solution.

For example: Na2SO3 and Na2S, if the temperature and the amount and concentration of the substance are the same, because the weak acid (H2S) corresponding to Na2S is weaker than the weak acid (H2SO3) corresponding to Na2SO3, so S2 - is easier to hydrolyze than SO32, and the alkalinity of the solution is stronger, and for example: the strength of the weak alkali corresponding to MgSO4 and Fe2(SO4)3 is different, and the alkalinity of Mg(OH)2 is stronger than Fe(OH)3, so the salt MgSO4 and Fe2(SO4)3 are compared, Fe2 ( The SO4)3 solution is more acidic.

2 Concentration of saline solution:

The dilution solution can promote hydrolysis, move to the right, and increase the percentage of hydrolysis; If the concentration of salt is increased, the hydrolysis equilibrium shifts to the right, but the hydrolysis percentage decreases.

For example, when preparing FeCl3 solution, in order to prevent FeCl3 hydrolysis, the prepared solution is generally a saturated solution, so that the degree of hydrolysis is small and the turbidity phenomenon is avoided.

Note: Although the degree of hydrolysis of saturated FeCl3 is small, its solution is acidic, and when diluted, the degree of hydrolysis increases, but due to the decrease in its concentration, its acidity increases.

3 Temperature. The hydrolysis reaction of salt is an endothermic reaction, and increasing the temperature can promote the hydrolysis of salt, so that the hydrolysis equilibrium shifts to the right, and the hydrolysis percentage increases.

For example, when the FeCl3 solution is heated, the color of the solution deepens and gradually becomes turbid, and eventually precipitation appears, but the acidity of the solution is enhanced by the increase of hydrolysis.

Another example: Na2CO3 solution, phenolphthalein is added at room temperature, the solution is light red, when heated, the red color of the solution gradually deepens, the degree of hydrolysis of salt increases, and the pH of the solution increases.

4 Acidity and alkalinity of the solution.

The ions that make up the salt can undergo a hydrolysis reaction with water, adding H+ to the salt solution can inhibit cation hydrolysis and promote anion hydrolysis, and adding oh- to the salt solution can inhibit anion hydrolysis and promote cation hydrolysis.

For example, when preparing FeCl3 solution, a small amount of HCl is generally added to inhibit the hydrolysis of Fe3+, because Fe3++3H2O Fe(OH)3+3H+; When H+ is added, its concentration increases, the equilibrium shifts to the right, and the degree of Fe3+ hydrolysis decreases, if OH—, H+ reacts with OH-, the H+ concentration decreases, and the equilibrium in the solution moves to the right, promoting the hydrolysis of Fe3+, and precipitation will occur.

Rules: the weaker the more hydrolyzed, the hotter the more hydrolyzed, the thinner the more hydrolyzed, and the acid and base are added to inhibit or promote hydrolysis.

No. Weak acids are weak electrolytes that are not completely ionized in solution, let alone hydrolyzed. Glacial acetic acid, for example, is weakly ionized when dissolved in water, and there are a large number of HAC molecules and a very small amount of H+ and AC- in the solution.

At this time, even if there is AC-, the amount is very small, and its hydrolysis in solution can be ignored, and it is unlikely to affect the ionization of HAC.

What you say about ionization is greater than hydrolysis, and it is mostly discussed in salt solutions, especially acid salts of weak acids. The most common examples are NAHCO3 and NAHSO3. In the former, because the hydrolysis of HCO3- in water is stronger than ionization, the solution is alkaline; The latter is acidic because the ionization of HSO3- in water is stronger than hydrolysis.

The strength of ionization and hydrolysis determines the acidity and alkalinity of the salt solution. If you want to memorize, just remember these two. Others will appear in the form of information in the question, and if you analyze it carefully, you can make an accurate judgment.

Basically, ionization is greater than hydrolysis because ionization is carried out first, and then hydrolysis can be carried out. But there are a few that are special.

This problem refers to the existence of ionization and hydrolysis of the same ion, such as: NaHSO3 and NaH2PO4 have two equilibrium of ionization and hydrolysis in aqueous solution. The degree of ionization is greater than hydrolysis, and the solution is acidic.

However, the hydrolysis of NaHCO3 and Na2HPO4 in aqueous solution is greater than ionization, and the solution is alkaline.

For a single weak acid. Only ionization equilibrium exists.

There is also a situation that the same concentration of weak acid and its sodium salt solution is generally more ionized than hydrolyzed, and the solution is acidic. However, there are exceptions, such as the concentration of HCN-NaCN solution is alkaline, and the hydrolysis is greater than the ionization.

Can you not talk nonsense, oxalic acid? I'm really.

Hydrolysis refers to the reaction that occurs when weak electrolyte ions bind to water in water. For example: acetate + water = acetic acid + hydroxide.

At this point, the solution appears alkaline. Double hydrolysis means that the solution contains both weak electrolytes and anions, and the anions and cations will be completely hydrolyzed. For example:

Bicarbonate + ammonium = water + carbon dioxide + ammonia. Metathesis reaction refers to the absence of valency change and is often accompanied by precipitation in aqueous solution.

Hydrolysis, that is, the hydrolysis of salts, is a reaction in which strong alkali and weak salts, strong acid and weak alkali salts, and weak acid and weak alkali salts combine their ionized ions with the ions ionized by water to form a weak electrolyte.

Double hydrolysis, that is, the anions and cations of a certain salt can be hydrolyzed, one is acidic, the other is alkaline, the two promote each other, the degree increases, if the gas and precipitation are generated, it can be carried out thoroughly.

Metathesis is a reaction in which two compounds, acids, bases, and salts exchange components with each other to produce two other compounds. There is gas, precipitation, weak electrolyte formation.

Ionization, refers to the process of ionization of electrolytes into ions under the action of water molecules in an aqueous solution, which is not a chemical change.

Note that the essence of the knowledge of "double hydrolysis" is:

1. As long as the cation of weak acid and the cation of weak alkali meet, as long as precipitation reaction, redox reaction and complexation reaction do not occur, double hydrolysis reaction will occur.

2. There are two types of double hydrolysis reactions: "can be carried out to the end" and "cannot be carried out to the end", and the double hydrolysis that can be carried out to the end must meet the weak acid and weak alkali generated by hydrolysis without reaction, otherwise it is "can not be carried out to the end"."Finish.

The final answer is A

1. The condition of a is insufficient, it should be indicated how many liters of the solution are diluted to 2L.

B is wrong, the acid is still acidic after dilution, pH < 7

C is wrong, sulfuric acid diluted 100 times with pH = 4, pH = 6, and the concentration of hydrogen ions produced by water ionization is the same as the concentration of hydroxides, which is minus 8 to the power of 10.

D is wrong, the alkali redilution solution is still alkaline, and the pH cannot be less than 7.

2. Select a water ionization to produce hydrogen ion concentrations less than 10 to the minus 7 power, so it is known that acid or alkali is added to resist the ionization of water, so a is selected.

The hydrolytic essence of ammonium ions in b is to promote the ionization of water. c Without hydrolysis, the concentration of hydrogen ions produced by water ionization is the same as that of pure water, which is 10 to the minus 7th power.

3. Choose AA, for hydrochloric acid, because it reacts with sodium acetate, the concentration of hydrogen ions decreases and the pH increases. In the case of acetic acid, the acetate ions produced by its ionization resist the ionization of acetic acid, and the concentration of hydrogen ions decreases and the pH increases.

In b, the pH of hydrochloric acid remains unchanged, but acetic acid is a weak acid, there is ionization equilibrium, the temperature equilibrium is positively shifted, the concentration of hydrogen ions increases, and the pH decreases.

c. After diluting with water, the acidity of the acidic solution will weaken and the pH will increase.

d. Because hydrochloric acid is completely ionized, and acetic acid is a weak acid, only a small amount of ionization, when the pH is the same, the concentration of acetic acid is much greater than that of hydrochloric acid, and when reacting with sufficient zinc, the hydrogen produced by acetic acid is much greater than that of hydrochloric acid.

(1) A Remember that an acid or base is still an acid or base no matter how diluted it is.

2) d sulfur dioxide solution, ammonium chloride aqueous solution is acidic pH less than 7 sodium nitrate aqueous solution 4 sodium hydroxide aqueous solution.

It is alkaline pH greater than 7

3) A After diluting twice with water, the pH of the two solutions increases After adding enough zinc to fully reflect, the acetic acid solution produces more hydrogen, because acetic acid is a weak acid.

CH3COOH solution with pH = 3 and NaOH solution with pH = 11 are mixed in equal volumes, and the two cannot react exactly completely, and acetic acid will be left behind. The so-called "exactly complete reaction" of an acid-base refers to a reaction according to the ratio of the quantities of the substances expressed in the equation.

Ammonium bicarbonate is an acid salt. The aqueous solution of acid salt is not necessarily acidic, for example, NH4HCO3 solution is weakly alkaline, sodium bicarbonate solution is weakly alkaline, and sodium bisulfite solution is weakly acidic.

Because what is generated is not necessarily a strong base or strong salt. Whoever is weak is hydrolyzed, and who is strong shows whose nature.

1. It happens to be completely reacted--- exactly according to the coefficient ratio of the equation.

2. Acid salt. NH4HCO3 is formed by the reaction of 1mol ammonia and 1mol carbonic acid, ammonia is a monobasic base, and carbonic acid is a dibasic acid, and the acid is excessive.

3. Because there is an error in the discoloration range of the acid-base indicator, methyl orange is; Phenolphthalein is 8--10

1 is the reaction to produce sodium acetate, acetic acid and sodium hydroxide have no remaining, C(Na+)>C(CH3Coo-)>C(OH-)>C(H+)

2 Acid salts, cations (volatile electrons) formed during ionization are hydrogen ions in addition to metal ions [or NH4+ (with metal ion properties)], and anions (easily obtained electrons) are salts of acid ions. This is the definition, i.e. after ionization, HCO3- contains H. It should be distinguished from acidic salts.

3 Because the indicator is not exactly 7, and a drop cannot make the pH equal to 7, it is a mutagenesis process.

1. One-to-one reaction ion concentration: Na+>CH3CoO->OH->H+2, acid salt Alkaline salt is one with hydroxide in it.

For example, Cu2(OH)2CO3

3. There is a range of titration endpoints, which are counted in that range, and a little more than half a drop near pH=7 will cause a relatively large change in pH, so generally pH=4-10 seems to be the endpoint.

You misunderstood, the equilibrium constant is the ionic product of hydroxide and hydrogen ions in solution, not water-ionized.

The lower the pH, the ionization of the water is inhibited, so the b pair.

First of all, it is necessary to understand the problem of the ion product of water at room temperature.

kw= is a constant, that is, the product of c(h+)*c(oh-) in any solution is a constant kw

mol l.

In the H2SO4 solution, the concentration of H+, theoretically, should indeed include the sum of the ionization of H2SO4, and the concentration of H+ resulting from the ionization of H2O, but, according to.

Chemical equilibrium. Obviously, the ionization of H2O is extremely weak, because the ionization of H2SO4 inhibits the ionization of H2O by a large amount of H+, so in this case, the concentration of H+ is approximately equal to the concentration of H+ produced by H2SO4 ionization!

From this, c can be found

oh-kw/c

H+, while in a strong acid solution, the only ** of OH- is.

Ionization of water. According to chemistry.

Conservation. Find C

oh-, then we can know the concentration of H+ produced by water ionization, because how much OH- is produced by water ionization

At the same time, there will inevitably be a large amount of H+.

In this question, H2SO4 is ionized and produced.

mol l of h+, so, c

OH-KW, which is also the concentration of H+ produced by water ionization.

About you. The question adds that you don't understand that the product of ions in water, at room temperature, is true for any solution, and refers to the product of the concentrations of "total H+" and "total oh-" in the "solution!!